Researches On The Relation Of Toxoptera Citricidus And Cirtus Tristeza Disease Epidemic

Citrus tristeza disease, caused by Citrus Tristeza Virus is a worldwide disease of citrus. Tristeza has seriously destroyed the citrus industry which had once got close to the breakup in South America nations such as Brazil. In recent years, CTV is more serious in some species as China changing citrus species structure. In china, pumelo and sweet orange are seriously infected by CTV with stem pitting symptom in Zhejiang, Sichuan and Guangxi province. CTV is spreaded mainly through grafting and aphid in the field, and Toxoptera citridus, which is dominant, is the best efficient transmitting vector. Researches on aphid and epidemic of CTV are of great importance to the control of Citrus Tristeza disease. In order to clear the aphid and Citrus tristeza disease epidemiology, in this research, to determine the dominant stocks of aphid on citrus by investgatting the occurrence and the damage of the aphids; to clear the relation of aphids and citrus tristeza disease epidemic by analysissing the identity and the efficiency of T. citridus transmitting CTV and the factors of influcing the efficiency; to detect the Citrus Tristeza Virus in aphids by molecular biology.Investigating the species of aphids by the methods numbering on one leaf. From the spring of 2004 to the autumn of 2005, investigate the citrus yard of garden College and XianjianVillage, the aphids number is 60-500 a tender leaf Evenly. And T. citridus is the dominant stocks. In the area of survey , T. citridus is dominant, and there are also some Aphid gossypii, Aphid citricola and Myzus persicae in the spring .The transmitting efficiency is different in the different condition.The transmitting efficiency and aphids number are in a coincidence. In this research, one aphid transmitting efficiency is 8% wihile 30 aphids' can get to 75%. The transmitting efficiency is more than 50% for 24 hours' acquisition while just 12% for 4 hours' by 10 aphids. The efficiency is 60% at 29℃ while only 12% at 35℃.To transmit CTV, the adult aphids are better than the young aphids.There are many factors influcing transmitting efficiencey. The efficiency of adults and the young is different. Besides, the variety of source plants and receptor plants can influence the aphids transmitting CTV. High temperature will drop off the aphid acquisition ability and the quantity of CTV particles, especially in summer.The detection of aphid acquiring CTV under serology and molecular biology. The former is not accurate and the latter is precise.